1. Field of the Invention
The present invention relates generally to an apparatus used for treating a semiconductor wafer with heat in wafer fabrication processes, and more particularly, to an apparatus for improving the uniformity of wafer heating as well as preventing the breakage and the warpage of the wafer.
2. Description of the Related Art
In numerous processes of the wafer fabrication, a heat treatment process of the wafer is necessary to form various layers, e.g., a metal layer, a polysilicon layer and so on. One kind of the heat treatment process is performed using a furnace in which the wafer is slowly heated. On the other hand, rapid thermal processing (RTP) techniques use heating lamps such as infrared lamps to allow for rapid wafer heating.
The RTP techniques have many advantages such as a high heating rate, easier temperature control, and reduced thermal budget. Currently, the RTP techniques are used in various phases of the wafer fabrication processes including silicide anneals, implant and other dopant activation, borophosphosilicate glass (BPSG) reflow, rapid thermal nitridation, hardened oxides, reoxidation, and implant and diffusion monitors.
In general, The RTP apparatus is composed of a supporting base for supporting the wafer mounted thereon, and a heating unit having several heating lamps for heating the wafer. Two examples of the conventional RTP apparatus are respectively shown in FIGS. 1 and 2.
Referring to FIG. 1, a semiconductor wafer 10 is mounted on a supporting base 101. A heating unit 105 has a plurality of stick-type infrared lamps 109 to apply heat to the wafer 10. The stick-type infrared lamps 109 are arranged at regular intervals over and under the wafer 10. However, with this arrangement of the infrared lamps 109, it is not easy to heat the wafer 10 in a uniform manner.
Referring to FIG. 2, the wafer 10 is mounted on a rotatable supporting base 103, which rotates horizontally on an axis. A heating unit 106 has a plurality of bulb-type infrared lamps 111 to apply heat to the wafer 10. The heating unit 106 is located above the wafer 10, and the bulb-type infrared lamps 111 are arranged densely at the bottom of the heating unit 106. This arrangement of the infrared lamps 111 serves to increase the uniformity of wafer heating. However, the rotation of the wafer 10 causes the breakage of the wafer 10, e.g., a crack at edges of the wafer 10, and the warpage of the wafer 10.
Accordingly, there is an immediate need for a heat-treating apparatus that not only improves the uniformity of wafer heating but also prevents the breakage and the warpage of the wafer.